Field of the Invention
The present invention relates to a fan assembly and a water heater and particularly to a fan assembly and a water heater which can be reduced in size.
Description of the Background Art
In replacement of an already placed tank water heater with an instantaneous water heater, there are locations where an already placed exhaust pipe (a B vent) cannot be removed from a point of view of maintaining appearance of buildings.
At such a location, a water heater can be replaced by leaving the already placed exhaust pipe and inserting an exhaust tube (a flexible exhaust tube) in the exhaust pipe. The exhaust tube should be smaller in diameter, because the exhaust tube cannot be placed in the exhaust pipe if the exhaust tube has a large outer diameter. In order to maintain a stable combustion state even when the exhaust tube is decreased in diameter, an exhaust suction and combustion system should be adopted for a water heater.
A water heater adapted to this exhaust suction and combustion system is disclosed, for example, in Japanese Patent Laying-Open No. 60-186617. In the water heater described in this publication, a heat exchanger for recovering sensible heat, a heat exchanger for recovering latent heat, and a fan are arranged in this order on a downstream side in a flow of combustion gas produced in a burner. Namely, in the water heater of this type, the fan is arranged downstream of the heat exchanger for recovering latent heat in the flow of combustion gas.
A centrifugal fan is available as a fan made use of in a water heater. For example, Japanese Patent Laying-Open No. 2005-291049 discloses a fan in which an impeller is accommodated in a fan case. In such a fan, the fan case mainly has a suction port opening in a direction of a rotation shaft of the impeller, an emission port opening in an outer circumferential direction of a blade, and a tongue portion. According to such a structure, as the impeller rotates, gas such as air is suctioned through the suction port and suctioned gas is emitted through the emission port.
In mounting the fan described above on a water heater adapted to an exhaust suction and combustion system, the fan case and the exhaust tube described above are connected to each other through the emission port. In order to reduce a size of such a water heater, the fan and components therearound should be reduced in size by providing the fan and the exhaust tube at positions in proximity to each other in a plan view from a direction of axis of the rotation shaft of the fan.
As a result of review by the present inventors, however, it has been found that blowing capability of the fan lowers when the fan case is designed simply such that the fan and the exhaust tube are proximate to each other in the water heater adapted to the exhaust suction and combustion system.